Stack folding implements are not broadly new. Typically, such implements comprise planters in which the openers must remain in a generally level condition when the frame is folded up so that the contents of the individual seed and fertilizer boxes will not be spilled. Prior machines are typically equipped with a center section and a pair of wing sections on opposite sides of the center section, with each wing being approximately half as wide as the center section. Thus, when the two wings are folded up into their stacked positions overlying the center section, they come into side-by-side relationship with one another to greatly reduce the total width of the machine. However, because the wings are positioned above the center section, the machine is significantly taller than it was in the unfolded condition, and in some prior machines portions of the wings or the folding mechanism still project outwardly beyond the center section to some extent.
Prior stack folding machines have utilized two sets of four-bar linkages between the center section and the wings to keep the wings generally level as they are lifted and lowered between their transport and working positions. However, the design of previous machines is such that when the wings are disposed in their stacked positions, there is a large amount of wasted space between the center section and the overhead wing sections. Thus, the transport height of the machine is excessive.